ES2715702T3 - Flame retardant polypropylene composition - Google Patents

Abstract

Flame retardant composition comprising: a) a base resin comprising a heterophasic propylene copolymer comprising a polypropylene homopolymer or copolymer matrix and an ethylene propylene rubber dispersed in said matrix, and b) a metal hydroxide, in which the copolymer of Heterophasic propylene has a fluidity index, measured at a temperature of 230 ° C and a load of 2.16 kg, according to ISO1133, below 0.8 g / 10 min and a fraction content soluble in cold xylene (XCS) between 1 and 15% by weight, based on the total weight of the heterophasic propylene copolymer and in which the base resin and metal hydroxide constitute 90% by weight of the total composition.

Description

DESCRIPTION

Flame retardant polypropylene composition

The present invention relates to a flame retardant polypropylene composition comprising a base resin and a metal hydroxide.

The present invention also relates to a wire or cable, in particular to a conduction, household and / or automobile cable comprising said composition, and to a process for the production of said wire or cable.

Driving cables, appliances or cars are cables that, apart from a conductive core and an optional thin layer, often only have a polymer layer. This layer must fulfill several functions at the same time, which in other low voltage cables, medium and high voltage cables are fulfilled by separate layers. These functions include those of an insulation layer and a protective outer cover.

Therefore, a polymer composition used for the production of conduction cables, appliances or automobiles must meet several demanding requirements at the same time, including good insulation behavior, good mechanical properties, in particular good abrasion resistance , good flame retardant properties, good resistance to heat deformation, resistance to cold temperatures, resistance to water and chemicals, as well as good processing properties.

As mentioned, optionally, the conductive, household and / or automobile layer may also have a coating layer that may be colored. However, said coating layer does not contribute significantly to fulfilling the requirements and fulfilling the functions mentioned above. In some cases, the conductive, household or automobile layer may further comprise a thin layer to increase abrasion resistance.

Polyvinyl Chloride (PVC) has been widely used for the coating of conduction cables, appliances or automobiles in automobile applications. The reason for its use is that PVC has good mechanical stability, conformability through extrusion, flexibility and resistance to wear and flame. On the other hand, due to environmental considerations, the use of PVC is not desirable due to its halogen content, as well as the release of toxic and corrosive gases during combustion. In addition, automotive cables are classified into temperature classes, which means that the cable must be able to withstand continuous heat. For example, in class T3, the cable must withstand a continuous temperature of 125 ° C, which is too high for normal PVC cables.

For these reasons, there has been a tendency to replace PVC in automotive applications with polyolefin compositions. However, polyolefins are inherently combustible materials and, since high flame resistance is required for automobile wires and cables, the flame resistance of these polyolefin compositions is obtained with specific additives.

In order to obtain polyolefin compositions with improved flame resistance, it is known, for example, that halogen-based chemicals or phosphate-based chemicals are incorporated into the composition. However, each of these additives has drawbacks, such as incompatibility with polyolefin, water solubility, the presence or emission of harmful, toxic or undesirable compounds and / or high costs. Since the composition must be able to withstand operating temperatures of up to 125 ° C (class T3), cross-linked polyethylene (PE) or polypropylene (PP) compositions are used for these applications. A thermoplastic compound such as PP has the advantage that the cables do not need to be crosslinked and, therefore, is preferred. However, since the PP becomes brittle at approximately -5 ° C, it is difficult to find a formulation that meets all the requirements of the specifications.

US 6673855 B1 discloses a polyolefin composition with high flame resistance comprising from 20 to 60% by weight of a heterophasic olefin polymer composition comprising a crystalline olefin polymer (A) and an olefin polymer elastomeric (B), from 15 to 40% by weight of one or more hydrated inorganic fillers (C), from 12 to 40% by weight of one or more retardants of organic flames containing nitrogen, and (D) from 0 to 40% by weight of one or more inorganic anhydrous fillers.

US 2002/0045698 A1 discloses a wear-resistant resin composition containing (A) 100 parts by weight of a modified micromix obtained by joining an organic acid group to a micromix composed of 1 to 70% by weight of polypropylene and 99 to 30% by weight of a random propylene-ethylene copolymer consisting of 15 to 50% molar of an ethylene polymer unit and 85 to 50 molar% of a propylene polymer unit, or a mixture of the micromix and the modified micromix, and (B) from 1 to 1,000 parts by weight of at least one load of a fibrous load or a laminar load, the mixture contains 10 to 90% by weight of a component that eluted at a temperature of -40 to 30 ° C, based on the total of all the eluted components fractionated by elution fractionation by temperature increase, using o-dibromobenzene as solvent.

US 2008/0306198 A1 discloses a thermoplastic polyolefin composition comprising 30-70% by weight of a heterophasic propylene polymer, 20-60% by weight of an ethylene copolymer with a comonomer selected from the group that comprises C3-6 aP-unsaturated carboxylic acids, C1-8 alkyl esters of a C3-6 aP-unsaturated carboxylic acid and mixtures thereof, and 2-20% by weight of a metal compound selected from the group comprising acetates, stearates, hydroxides and oxides of zinc, magnesium, calcium, sodium and mixtures thereof.

WO 2013/030795 A1 discloses a process for the production of a flame retardant composition that includes a matrix polymer and at least one inorganic filler with flame retardant properties.

US 2011/0253420 A1 discloses a flame retardant polymer composition comprising (A) an ethylene copolymer comprising polar comonomer units, (B) a compound containing a silicone group, (C) an inorganic filler and (D) an ethylene homopolymer or an ethylene copolymer with one or more alpha-olefin comonomer units, wherein the polymer composition has a melting enthalpy of at least 78 J / g.

US 2014/0080953 A1 discloses highly charged flexible polyolefin compositions with an improved balance of properties, particularly, for applications where softness and low temperature ductility are required, comprising a soft heterophasic polyolefin composition, having the xylene soluble fraction at 25 ° C of said polyolefin composition an IV gpc of less than 2.5 dl / g, an Mw / Mn (GPC) equal to or greater than 4, an Mz / Mw (GPC) equal to or greater than 2.5 The polyolefin composition further comprises an inorganic filler (II) selected from inorganic fillers retarding the flames and inorganic oxides or salts and an additional elastomeric polymer or a polymeric component (c) having a flexural modulus of less than 60 MPa, Shore At less than 90 and Tg less than -20 ° C.

EP 1857502 discloses a flame retardant composition comprising polypropylene, a polar ethylene and a metal hydroxide. The compositions have good abrasion resistance and good flame retardation and are suitable for automobile cables of more than 0.7 mm2. However, for thinner wires, smaller than 0.7 mm2 or equal to this surface, the demanding specification requirements can no longer be satisfied with these compositions.

Therefore, an objective of the present invention is to disclose compositions that have good flame retardation and, at the same time, cold flexibility, thermooxidative aging, aging in combination with different media, abrasion resistance. In particular, the compositions must meet the new GM specifications (GM15626) and the German standard (LV112) that have resistance to needle abrasion as a mandatory requirement.

Now, it has been discovered that the objective of the present invention can be achieved by a composition comprising:

a) a base resin comprising a heterophasic propylene copolymer comprising a polypropylene homopolymer or copolymer matrix and an ethylene propylene rubber dispersed in said matrix, and b) a metal hydroxide,

in which the heterophasic propylene copolymer has an MFR2 below 0.8 g / 10 min and a cold xylene soluble fraction (XCS) content of between 1 and 15% by weight, based on the total weight of the heterophasic propylene copolymer, and in which the base resin and metal hydroxide constitute 90% by weight of the total composition.

In general, a heterophasic polypropylene is a propylene copolymer comprising a propylene homopolymer or a random propylene copolymer matrix component and an elastomeric propylene copolymer component with one or more of ethylene and / or C4-a-olefin copolymers. C8, wherein the elastomeric (amorphous) copolymer is dispersed in said propylene homopolymer matrix polymer or random copolymer thereof. The elastomeric phase contains a propylene copolymer rubber, such as an ethylene propylene rubber (EPR). In the present invention, the rubber component is a copolymer of propylene and ethylene and is mainly in amorphous form, measured as cold xylene solubility (XCS).

The XCS fraction of said heterophasic propylene copolymers comprises, in addition to the total amount of rubber dispersed within the matrix, also amorphous parts of the polypropylene matrix. However, in common practice, the XCS fraction is used to indicate the total amount of rubber of the heterophasic propylene copolymer, since the amount of XCS fraction in the matrix component is markedly smaller.

In the context of the present invention, "rubber" and "copolymer / fraction / elastomer component" are used as synonyms.

Here, the term "base resin" is intended to define all polymeric components of the composition of the present invention.

According to one embodiment, the base resin comprises 90% by weight, preferably 95% by weight or 98% by weight and even more preferably, 99% by weight of the heterophasic propylene copolymer, based on the total weight of the base resin. Preferably, the base resin does not contain any polar ethylene copolymer.

According to a preferred embodiment, the base resin comprises the heterophasic propylene copolymer. This is specifically advantageous for thinner cables, equal to or less than 0.7 mm2.

According to another preferred embodiment, the base resin further comprises a polar ethylene copolymer.

Preferably, the base resin, and therefore also the total composition, is free of any grafted polypropylene component, since having grafted polypropylene generates high costs.

Preferably, the composition is free of compounds containing halogen and phosphorus as flame retardants. More preferably, the composition is completely free of halogen-containing compounds. However, phosphorus-containing compounds may be present in the composition as stabilizers, generally in an amount less than 5000 ppm, more preferably, less than 2500 ppm.

The components of the composition may comprise a single compound or may also comprise a mixture of different compounds of the same category.

The heterophasic propylene copolymer comprises a polypropylene homopolymer or copolymer as the matrix polymer and an ethylene propylene rubber dispersed in said matrix or consists thereof.

According to a preferred embodiment, the matrix in the heterophasic propylene copolymer is produced from propylene homopolymer.

The heterophasic copolymer, according to the present invention, has a cold xylene soluble fraction content of 1 to 15% by weight, more preferably, 4 to 13% by weight, based on the total weight of the heterophasic propylene copolymer.

Preferably, the heterophasic propylene copolymer has a total amount of ethylene between 1 and 8.5% by weight, preferably between 1 and 7% by weight, more preferably between 1 and 5% by weight, based in the total weight of the heterophasic propylene copolymer.

The ethylene-propylene rubber, apart from the ethylene and propylene monomer units, may contain other alpha-olefin monomer units. However, it is preferred that the ethylene propylene rubber consists of ethylene and propylene monomer units.

Preferably, the melting temperature of the heterophasic propylene copolymer is greater than 150 ° C, more preferably, greater than 160 ° C.

The heterophasic propylene copolymer has an MFR2 greater than 0.1 g / 10 min and below 0.8 g / 10 min, preferably below 0.5 g / 10 min.

The heterophasic propylene copolymer can be produced by a multistage process of polymerization of propylene and ethylene and, optionally, alpha-olefin, such as mass polymerization, gas phase polymerization, suspension polymerization, solution polymerization or combinations of the same using conventional catalysts. The heterophasic copolymer can be manufactured in loop reactors or in a combination of loop reactor and gas phase. These procedures are well known to those skilled in the art.

A preferred method is a combination of a bulk suspension reactor or loop reactors and a gas phase reactor or reactors. First, the propylene homopolymer or copolymer matrix is produced in one or more loop reactors or in a combination of loop reactor and gas phase.

The polymer produced in this way is transferred to another reactor and the dispersed phase, the ethylene-propylene rubber, is produced by copolymerizing a mixture of ethylene and propylene with the same catalytic system, obtaining a heterophasic system consisting of a matrix semi-crystalline with an elastomeric component amorphous scattered within it. Preferably, this polymerization step is carried out in a gas phase polymerization.

A suitable catalyst for the polymerization of the heterophasic copolymer is any stereospecific catalyst for the polymerization of propylene which is capable of polymerizing and copolymerizing propylene and comonomers at a temperature of 40 to 110 ° C and a pressure of 10 to 100 bar. Ziegler-Natta catalysts, as well as metallocene catalysts, are suitable catalysts.

Alternatively, to produce the heterophasic copolymer in a multi-stage sequential process, as described above, it can be produced by polymerization of the matrix polymer and ethylene-propylene rubber in separate steps and by melting the two polymers .

To further improve processability and melt strength, the flame retardant composition may preferably comprise a polypropylene that exhibits deformation hardening behavior. This polypropylene, for example, is described in EP 1301343. The definition of "deformation hardening behavior" is given in paragraphs [0008] to [0010] of this document. As mentioned in the aforementioned document, a polypropylene showing a strain hardening behavior is defined as having a stretching force greater than 15 cN and a stretching capacity with a stretching speed greater than 150 mm / s in the test, as described in detail in EP 1301343 and as illustrated in Figures 1 and 2 thereof.

An elastomeric ethylene propylene copolymer can be produced by known polymerization processes such as solution, suspension and gas phase polymerization using conventional catalysts. Ziegler-Natta catalysts, as well as metallocene catalysts, are suitable catalysts.

A widely used procedure is solution polymerization. The ethylene, propylene and catalyst systems are polymerized in an excess of hydrocarbon solvent. Stabilizers and oils, if used, are added directly after polymerization. The solvent and unreacted monomers are removed by evaporation with hot water or steam, or with mechanical devolatilization. The polymer, which is in the form of lumps, is dried with dehydration in sieves, mechanical presses or drying ovens. The lumps are formed in wrapped bullets or extruded into granules.

The suspension polymerization process is a modification of the bulk polymerization. The monomers and the catalytic system are injected into the reactor filled with propylene. The polymerization takes place immediately, forming lumps of polymer that are not soluble in the propylene. Sudden evaporation of propylene and the comonomer completes the polymerization process.

The gas phase polymerization technology consists of one or more vertical fluidized beds. The monomers and nitrogen are fed into the reactor in gaseous form together with the catalyst and the solid product is periodically removed. The heat of reaction is eliminated by using the circulating gas that also serves to fluidize the polymer bed. No solvents are used, which eliminates the need to remove, wash and dry the solvents.

The production of elastomeric copolymers of ethylene propylene is also described in detail, for example, in US 3,300,459, US 5,919,877, EP 0060090 A1 and in a company publication by EniChem "DUTRAL, Ethylene-Propylene Elastomers" , pages 1-4 (1991).

Alternatively, elastomeric ethylene-propylene copolymers can be used, which are commercially available and that meet the stated requirements.

The heterophasic copolymer is then produced by combining the matrix polymer in powder or granule form and the elastomeric copolymer in a melt mixing device.

In the case where a random polypropylene copolymer is used as the matrix polymer for the heterophasic copolymer, the comonomers are preferably linear alpha-olefins or branched alpha-olefins, such as ethylene, butene, hexene, etc. In the present invention, ethylene is the most preferred. Preferably, the comonomer content is 10% by weight or less, more preferably it is between 4 and 8% by weight, based on the total random polypropylene copolymer.

However, preferably, the matrix polymer is a polypropylene homopolymer.

Preferably, the base resin a) is present in the composition in an amount of 30 to 52% by weight, more preferably, 39 to 45% by weight or 40 to 45% by weight, based on the weight of the total composition .

The base resin may further comprise a polar ethylene copolymer.

The polar ethylene copolymer is preferably produced by copolymerization of ethylene monomers with appropriate comonomers having polar groups.

It is preferred that the polar copolymer comprises an ethylene copolymer, with one or more comonomers selected from C1 to C6 alkyl acrylates, C1 to C6 alkyl methacrylates, hydroxyl-functional monomers, for example, 2-methylated (meth) acrylate -hydroxyethyl, acrylic acids, methacrylic acids, vinyl acetate and vinyl silanes. For example, the polar copolymer can also be an terpolymer of ethylene, one of the monomers mentioned above and a vinyl silane. The copolymer may also contain ionomeric structures (such as in DuPont's Surlyn types).

Even more preferably, the polar copolymer is an ethylene / acrylate and / or ethylene / acetate copolymer.

More preferably, the polar polymer comprises a copolymer of ethylene with C1 to C4 alkyl, such as methyl, ethyl, propyl, i-butyl or n-butyl, acrylates or vinyl acetate. In a particularly preferred embodiment, the polar comonomer is butyl acrylate. In a particularly preferred embodiment, the polar polyethylene is a copolymer of ethylene butyl acrylate (EBA).

In addition to ethylene and defined comonomers, the copolymers may also contain other monomers. For example, terpolymers between acrylates and acrylic acid or methacrylic acid, or acrylates with vinylsilanes, or acrylates with siloxane, or acrylic acid with siloxane can be used.

These copolymers can be crosslinked after extrusion, for example, by irradiation. Silane crosslinkable polymers can also be used, that is, polymers prepared using unsaturated silane monomers having hydrolysable groups capable of crosslinking by hydrolysis and condensing to form silanol groups in the presence of water and, optionally, a silanol condensation catalyst.

Preferably, the amount of comonomer units with polar groups in the polar ethylene copolymer is 0.5% by weight or more, more preferably, it is 1.0% by weight or more and, most preferably, it is 2.0% by weight or more.

In addition, the amount of comonomer units with polar groups in the polar ethylene copolymer is preferably 30% by weight or less, more preferably, is 20% by weight or less and, most preferably, is 17% by weight or less.

Preferably, the polar ethylene copolymer is present in the composition in an amount of 1 to 30% by weight, more preferably, 5 to 20% by weight, based on the weight of the total composition.

The melt index MFR2 of the polar ethylene copolymer is preferably 15 g / 10 min or less, more preferably, it is 10 g / 10 min or less, even more preferably, it is 5 g / 10 min or less, even more preferably, it is 2 g / 10 min or less and, most preferably, it is 1 g / 10 min or less.

In the flame retardant polypropylene composition, according to the present invention, component b) is preferably present in an amount of 47 to 62% by weight, preferably 52 to 62% by weight, based on the weight of The total composition.

In the case that the base resin consists of the heterophasic propylene copolymer, then, more preferably, the heterophasic propylene copolymer is between 55 and 60% by weight, based on the weight of the total composition.

The polymer composition, according to the present invention, may further comprise an ethylene copolymer, preferably prepared by a single site catalyst, having a density between 0.860 and 0.910 g / cm 3. Preferably, the ethylene copolymer (B) has a density between 0.870 and 0.905 g / cm3, more preferably, between 0.875 and 0.900 g / cm3.

The ethylene copolymer can be prepared in a low pressure reactor by using a class of highly active olefin catalysts, known as metallocenes, preferably those based on transition metals of group IV B, zirconium, titanium and hafnium.

The ethylene copolymer suitably comprises comonomer units derived from C4 to C12 a-olefin, more preferably, C8 to C12 a-olefin. Even more preferably, the comonomer units of the ethylene copolymer consist of comonomer units derived from C4 to C12 a-olefin, more preferably, from C8 to C12 a-olefin. More preferably, the α-olefin is octane. Suitably, the ethylene copolymer has a melting point of at least 65 ° C and below 110 ° C.

The melt index, MFR2, of the ethylene copolymer is preferably 15 g / 10 min or less, more preferably, is 10 g / 10 min or less, even more preferably, it is 5 g / 10 min or less , even more preferably, it is 2 g / 10 min or less and, most preferably, it is 1 g / 10 min or less.

Preferably, the ethylene copolymer is present in the polymer composition in an amount between 2 and 30% by weight of the total polymer composition, preferably between 5 and 20% by weight.

Preferably, component b) comprises a metal hydroxide, more preferably it consists, more preferably, a metal hydroxide of a metal of groups 1 to 13, more preferably, of groups 1 to 3 of the periodic table of the elements . The numbering of chemical groups, as used herein, is according to the IUPAC system, in which the groups of the periodic system of the elements are numbered from 1 to 18.

Even more preferably, component b) comprises a hydroxide selected from the group of magnesium, calcium, potassium, barium and aluminum or magnesium, calcium and potassium, more preferably consists of them, and component b) most preferably comprises magnesium hydroxide, more preferably it consists of it. Preferably, the compound b) comprises a metal hydroxide, more preferably consists of it, which has been surface treated with an organosilane compound, a polymer, a carboxylic acid or salt, etc. to aid processing and provide a better dispersion of the hydroxide in the organic polymer. Such coatings usually do not constitute more than 3% by weight of the hydroxide. Examples of coated Mg (OH) 2 are Magnifin H5HV commercially available from Martinswerke, Germany, or Kisuma 5AU available from Kisuma Chemicals BV.

The base resin a) and the metal hydroxide b) constitute 90% by weight, preferably 95% by weight of the total composition.

Preferably, the base resin a) and the metal hydroxide b) constitute 90% by weight, preferably 95% by weight of the total composition, and the base resin a) is present in the composition in an amount between 35 and 60% by weight, preferably between 38 and 53% by weight or 38 and 48% by weight or 40 to 45% by weight and the metal hydroxide b) in an amount of 40 to 65% by weight or from 47 to 62% by weight, preferably from 52 to 62% by weight or from 55 to 60% by weight, based on the weight of the total composition.

According to a preferred embodiment, the base resin a) consists of the heterophasic propylene copolymer, the heterophasic propylene copolymer is present in the composition, preferably, in an amount between 40 and 45% by weight and the metal hydroxide b) in an amount of 55 to 60% by weight, based on the weight of the total composition.

In addition to the components mentioned above, the composition may contain additional ingredients, such as, for example, antioxidants and / or UV stabilizers, pigments, curing reinforcements, process aids, etc. In small quantities.

The flame retardant polymer composition of the present invention shows superior abrasion resistance, so it resists in the abrasion test according to ISO 6722 (0.45 mm needle diameter) in a cable with a cross section. 0.35 mm2 driver, 100 cycles or more.

The present invention further relates to a wire or cable comprising a layer made of the flame retardant polypropylene composition in any of the embodiments described above.

Preferably, the wire or cable is a conduction, household or automobile cable consisting of an inner conductor core surrounded by a flame retardant layer made of a polypropylene composition in any of the embodiments described above and, optionally, a coating layer

The flame retardant layer of said conduction, household or automobile cable preferably has a thickness of 0.1 to 4 mm.

In case there is an outer layer of coating, preferably, it has a maximum thickness of 0.6 mm. However, it is preferred that there is no coating layer present in the final cable, that is, that the insulation layer is the outermost layer.

Furthermore, the conductor area of said conduction, household or automobile cable is preferably 0.1 to 400 mm2.

The present invention further relates to a process for the production of a flame retardant layer of a wire or cable comprising forming in said layer a composition, in any of the embodiments described above, and to the use of the retarding polypropylene composition. of the flames, in any of the embodiments described above, for the production of the flame retardant layer of a wire or cable.

The flame retardant polymer composition that forms the cable or wire layer, according to the present invention can be prepared by:

i) the preparation of a mother mixture comprising additives and polymer followed by

ii) mixing with inorganic filler and matrix polymer, or a mixing stage of all components

For mixing, a conventional composition or mixing device can be used, for example, a Banbury mixer, a 2-roll rubber mill, a Buss co-mixer or a twin-screw extruder. Preferably, the composition will be prepared by mixing it at a temperature that is sufficiently high to soften and plasticize the polymer, typically a temperature in the range of 180 to 250 ° C.

The polymer composition is preferably extruded to form the flame retardant layer. This is preferably done at a linear speed of at least 20 m / min, more preferably at least 60 m / min and, most preferably, at least 100 m / min. Preferably, the pressure used for extrusion is 50 to 500 bar.

In the following, the present invention is further illustrated by way of examples.

1. Test procedures

a) Fluency index

The flow rate (MFR) is determined according to ISO 1133 and is indicated in g / 10 min. The MFR is an indication of the fluidity and, therefore, of the processability, of the polymer. The higher the flow rate, the lower the viscosity of the polymer. The polypropylene MFR2 is measured at a temperature of 230 ° C and a load of 2.16 kg. b) Delay of the flames

Flame retardation is measured according to ISO 6722: 2006, paragraph 12 (resistance to flame propagation).

The purpose of said test procedure is to determine the propagation resistance of the flames for automobile cables. The cable (600 mm) is installed at a 45 degree angle to the vertical line and a flame produced by a Bunsen burner, fed with an appropriate gas, which has a combustion tube of 9 mm internal diameter and a height of 100mm flames are applied to the cable sample at an angle of 90 degrees to 500mm from the top end of the insulation.

The test sample should be exposed to the tip of the inner blue cone of the flame that is 50 mm long. For cables that have a conductor size of 2.5 mm2 or less, the flame is applied for 15 seconds. To comply with the test, the flame must be extinguished within 70 seconds after removing the flame from the burner with a minimum of 50 mm of insulation from its top without burning. A cable that meets this criterion is marked "pass", otherwise it is marked "fail."

c) Scratch abrasion

The abrasion test is carried out according to ISO 6722: 2006, paragraph 9.3. The abrasion resistance as reported is based on the testing of a cable sample based on a 0.35 mm2 18 AWG stranded copper conductor with a nominal layer wall thickness of 0.24 mm (0.4 real mm). The needle diameters used are 0.45 mm, the force of 7 Newton and the samples analyzed are not crosslinked. The results are shown in table 3 and reported as cycles that the material can withstand. For each cable tested, twelve samples are analyzed and the average and minimum number of strokes are reported. If any of the samples withstand less than 200 strokes, it is reported as a failure in Table 3.

d) Cold xylene soluble fraction content (XCS)

The amount of cold xylene soluble fraction is determined according to ISO 16152. The amount of polymer that remains dissolved at 25 ° C after cooling is given as the amount of xylene soluble polymer. It is assumed that the content of polymer soluble in xylene follows the mixing rule:

XS ^b = W ⁱ XS ⁱ + W ² XS ²

Where XCS is the content of polymer soluble in xylene in% by weight, w is the fraction by weight of the component in the mixture and the subscripts b, 1 and 2 refer, respectively, to the general mixture, component 1 ( matrix component) and component 2 (elastomeric component).

e) Ethylene content as a total amount in the heterophasic propylene copolymer and as an amount only in the elastomeric phase.

The comonomer content is determined by quantitative Fourier transform infrared spectroscopy (FTIR) after the basic allocation calibrated by quantitative 13C nuclear magnetic resonance (NMR) spectroscopy, in a manner well known in the art.

Thin films up to a thickness of between 100 and 500 micrometers are prepared in the press and the spectra are recorded in the transmission mode. Specifically, the ethylene content of a polypropylene-co-ethylene copolymer is determined using the area of the corrected peak at the baseline of the quantitative bands found at 720-722 and 730-733 cm -1. Specifically, the butene or hexene content of a polypropylene copolymer is determined using the area of the corrected peak at the baseline of the quantitative bands found at 1377-1379 cm -1. Quantitative results are obtained based on the reference to the thickness of the film.

In this document, it is assumed that the comonomer content follows the following mixing rule:

where C is the comonomer content in% by weight, w is the weight fraction of the component in the mixture and the subscripts b, 1 and 2 refer, respectively, to the general mixture, component 1 (matrix component) and component 2 (elastomeric component).

As is well known to those skilled in the art, the comonomer content by weight in a binary copolymer can be converted to the molar comonomer content using the following equation:

where cm is the molar fraction of the comonomer units in the copolymer, cw is the weight fraction of the comonomer units in the copolymer, MW ^c is the molecular weight of the comonomer (such as ethylene) and MWm is the weight molecular of the main monomer (ie, propylene).

f) Density

Density is measured according to ISO 1183 on compression molded plates.

g) Flexural modulus

The flexural modulus is determined according to ISO 178.

Test samples having a dimension of 80 x 10 x 4.0 mm3 (length x height x thickness) are prepared by injection molding according to EN ISO 1873-2. The length of the section between the supports is 64 mm, the test speed is 2 mm / min and the force is 100 N.

h) Charpy impact resistance with notch

Notched Charpy impact resistance is determined according to ISO 179-1eA: 2000 in samples with V notches of 80 x 10 x 4 mm3 at 23 ° C, 0 ° C and -23 ° C as specified in the examples . The test samples are prepared by injection molding using an IM V60 TECH machinery in line with the EN ISO 1873-2 standard (80 x10 x 4 mm3). The melting temperature is 200 ° C and the mold temperature is 40 ° C.

i) Cold flexibility (low temperature winding test)

Cold flexibility is measured according to ISO 6722: 2006, paragraph 8. The cable is fixed in a rotating mandrel and placed in a freezing chamber at 40 ° C for 4 hours. After exposure, the test sample is allowed to return to room temperature and a visual inspection of the insulation is performed. If no exposed conductor is seen, a resistance test at a voltage of 1 kV is carried out for 1 minute. In the previous voltage test, the sample is immersed in a salt water bath for 10 minutes. The sample is marked as "passes" in table 3 if no exposed conductor or failure is observed during the tensile strength test.

j) Thermal overload in rolled state

The thermal overload is controlled, according to ISO6722: 2006, paragraph 10.3. The wire is placed in a 175 ° C heating oven for six hours, followed by conditioning for a minimum of 16 hours at room temperature, according to paragraph 10.1.4. Subsequently, the cable is placed in a mandrel defined in Table 8 of ISO6722: 2006. No conductor should be observed and, during the resistance voltage test, no breakdown will occur.

2. Examples

In the preparation of the compositions of the present invention (Ex 1-Ex 3), heterophasic propylene copolymers BA202E, BA212 ^e , available from Borealis AG and PP-EPR1, are used. PP-EPR1 is prepared as follows:

Catalyst preparation

First, 0.1 mol of MgCl2 x 3 EtOH is suspended under inert conditions in 250 ml of decane in an atmospheric pressure reactor. The solution is cooled to a temperature of -15 ° C. 300 ml of cold TiCU are added while maintaining the temperature at that level. Then, the temperature of the suspension is slowly increased to 20 ° C. At this temperature, 0.02 moles of diethylhexylphthalate (PDO) are added to the suspension. After the addition of the phthalate, the temperature rises to 135 ° C for 90 minutes and the suspension is allowed to stand for 60 minutes. Next, another 300 ml of TiCU is added and the temperature is maintained at 135 ° C for 120 minutes. After this, the catalyst is filtered from the liquid and washed six times with 300 ml of heptane at 80 ° C. Next, the solid catalyst component is filtered and dried. The catalyst and its preparation concept are generally described, for example, in patent publications EP 491566, EP 591224 and Ep 586390.

Next, triethylaluminum (TEAL), dicyclopentyldimethoxysilane (DCPDMS) is added as a donor (Do), catalyst as previously produced and vinylcyclohexane (VCH) in the oil, such as mineral oil, for example, Technol 68 (kinematic viscosity a 40 ° C 62-74 cSt), in quantities such that Al / Ti is 3-4 mol / mol, Al / Do is also 3-4 mol / mol, and a weight ratio of VCH / solid catalyst is 1: one.

The mixture is heated to 60-65 ° C and allowed to react until the unreacted vinylcyclohexane content in the reaction mixture is less than 1000 ppm. The concentration of catalyst in the final oil-catalyst suspension is 10-20% by weight.

Polymerization

In PP-EPR1, the matrix is made of a propylene homopolymer that is prepared in a loop reactor and a gas phase reactor (GPR1). The polymer obtained is stabilized with conventional stabilizer and antioxidant. The following table shows additional information on the propylene homopolymer that constitutes the matrix. Subsequently, the propylene homopolymer is transferred to a second gas phase reactor (GPR2) in which the elastomeric polypropylene is prepared. The polymer obtained is stabilized in a conventional twin-screw extruder with conventional stabilizers, that is, calcium stearate and phenolic antioxidant, in conventional amounts, and is granulated for further tests, as indicated in Table 1.

For the preparation of comparative compositions (EC1-EC4), polypropylenes HA507MO (propylene homopolymer), RA130E (random propylene copolymer) and heterophasic propylene copolymers BA125MO and BA204E, available from Borealis AG, are used.

Table 1

The properties of all polymers are listed in Table 2.

Table 2

The polymer compositions of all examples are produced by combining the polymers listed in Table 2 with Magnifin H5HV (Mg (OH) 2) from Martinswerke, Germany and with Irganox 1010, Irganox 1024 and Irganox PS 802 (antioxidants).

The amount by weight of each component for the examples of the present invention and comparative examples is provided in Table 3.

A Buss co-mixer type PR46B-11 D / H1 is used for mixing.

Table 3

Automobile cables of 0.35 mm2 (7 x single cables of 0.254 mm in diameter) are produced from the compositions in a Nokia-Maillefer extruder, 45 mm / 28D, with a temperature profile of: 165-185-200 -215-220 (Bride) -230 (Flansch) -235 (Bypass) -250 (Head) -250 ° C (Pressure row).

The outer diameter of the cable is 1.28 mm and the wall thickness is 0.24 mm.

The melting temperature is 220 ° C and a line speed of 100 m / min. The driver is preheated to a setting temperature of 90 ° C. The compound is previously dried for 18 hours at 80 ° C before extrusion. The properties of 0.35 mm2 cables are listed in Table 4. The tests are carried out, according to standards LV112 and ISO6722 (January 17, 2014).

Table 4

From table 4 it can be clearly seen that for the thin cables the required cycles of 200 strokes in the needle abrasion test only comply with the compositions of the present invention and comparative composition 3, which, however, shows lower properties at low temperatures. The other properties are best for inventive examples 2 and 3.

Therefore, it is shown that only specific types of heterophasic copolymers are suitable for automobile, conduction and home appliance cables.

Claims (13)

1. Flame retardant composition comprising: a) a base resin comprising a heterophasic propylene copolymer comprising a polypropylene homopolymer or copolymer matrix and an ethylene propylene rubber dispersed in said matrix, and b) a metal hydroxide, in which the heterophasic propylene copolymer has a fluidity index, measured at a temperature of 230 ° C and a load of 2.16 kg, according to ISO1133, below 0.8 g / 10 min and a content of cold xylene soluble fraction (XCS) between 1 and 15% by weight, based on the total weight of the heterophasic propylene copolymer and in which the base resin and metal hydroxide constitute 90% by weight of the total composition . 2. Composition according to claim 1, wherein the heterophasic propylene copolymer has a total amount of ethylene between 1 and 8.5% by weight, preferably between 1 and 7% by weight, based on weight Total heterophasic propylene copolymer. 3. Composition according to claim 1 or 2, wherein the flow rate, measured at a temperature of 230 ° C and a load of 2.16 kg according to ISO1133, of the heterophasic propylene copolymer is less than 0, 5 g / 10 min. 4. Composition according to any one of the preceding claims, wherein the base resin a) and the metal hydroxide b) constitute 95% by weight of the total composition. 5. Composition according to any one of the preceding claims, wherein the base resin a) is present in the composition in an amount between 30 and 52% by weight and the metal hydroxide b) in an amount from 47 to 62 % by weight, based on weight of the total composition. 6. Composition according to any one of the preceding claims, wherein the base resin consists of the heterophasic propylene copolymer. 7. Composition according to claim 6, wherein the heterophasic propylene copolymer is present in the composition in an amount between 40 and 45% by weight of the metal hydroxide b) in an amount of 55 to 60% by weight based in the weight of the total composition. 8. Composition according to any one of claims 1 to 5, wherein the base resin further comprises a polar ethylene copolymer. 9. Composition according to claim 8, wherein the polar ethylene copolymer is ethylene butyl acrylate (EBA). 10. Composition according to claims 8 or 9, wherein the polar ethylene copolymer is present in the composition in an amount between 2 and 30% by weight based on the weight of the total composition. 11. Composition according to any one of claims 1 to 5 or 8 to 10, wherein the base resin further comprises an ethylene copolymer having a density between 0.860 and 0.910 g / cm3. 12. Composition according to claim 11, wherein the ethylene copolymer is present in the composition in an amount between 2 and 30% by weight, based on the weight of the total composition. 13. Composition according to any one of the preceding claims, wherein the metal hydroxide b) comprises magnesium hydroxide.